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Showing content from https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Symbol/species below:

Symbol.species - JavaScript | MDN

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知名的 Symbol.species 是个函数值属性，其被构造函数用以创建派生对象。

class Array1 extends Array {
  static get [Symbol.species]() {
    return Array;
  }
}

const a = new Array1(1, 2, 3);
const mapped = a.map((x) => x * x);

console.log(mapped instanceof Array1);
// Expected output: false

console.log(mapped instanceof Array);
// Expected output: true

species 访问器属性允许子类覆盖对象的默认构造函数。

你可能想在扩展数组类 MyArray 上返回 Array 对象。例如，当使用例如 map() 这样的方法返回默认的构造函数时，你希望这些方法能够返回父级的 Array 对象，以取代 MyArray 对象。Symbol.species 允许你这么做：

class MyArray extends Array {
  // 覆盖 species 到父级的 Array 构造函数上
  static get [Symbol.species]() {
    return Array;
  }
}
var a = new MyArray(1, 2, 3);
var mapped = a.map((x) => x * x);

console.log(mapped instanceof MyArray); // false
console.log(mapped instanceof Array); // true

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